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The secrets of Seamless Shift Gearboxes in F1


By Eli (aka KineticKid)
May 8 2008

Over the past few seasons, the design of F1 gearboxes, and particularly the method by which gear selection takes place, have become dutifully protected team secrets. An area which has relied on rather traditional transmission concepts for several years has been the subject of re-design in the attempt to acheive what has been dubbed seamless shifts.

 Seldom have engineers privy to the workings of this new generation of gearboxes been forthcoming, furtively evading questions on the matter. For that reason, ascertaining information is exceedingly difficult as it pertains to how shifts can be made with minimal loss of drive, while at the same time smoothing torque spikes across the drivetrain. However, details have slowly emerged pointing to the use of two systems in F1: The Weismann Quickshift, first tested by Williams on the FW15, and it's successor, the Zeroshift transmission.

* Some photos and graphs of gearboxes can be found at http://www.f1network.net/main/s491/st128890.htm

First, we'll touch on some basics regarding the implications of the gearbox case. An F1 gearbox is a fully stressed member of the chassis. It is the point through which the rear wishbones and dampers are attached to the car. The rear crash structure is also mounted on the gearbox. Because the gearbox is situated relatively high in the chassis, ballast is affixed to the under-side of the box to improve the overall centre of gravity. As one would imagine the gearbox casing is incredibly robust, with teams opting from a range materials, such as carbon fibre, titanium, aluminum and magnesium. As a seamless shift gearbox carries an additional weight penalty of 1 to 2 kg in comparison to conventional box, this makes carbon fibre (the lightest of the options avaiable) an attractive option in order to offset the weight penalty. A combination of these materials is the solution employed by several teams. According to Autosport's 2007 technical review, Honda and McLaren were the only teams to use fully carbon fibre casings.

For teams who opt for a hybrid of materials, they must consider the rear suspension geometry and it's attachment points to the casing. In some cars, the gearbox panels are the stress bearing structure, where in others, it is the frame. For example, if the panels are the stress bearing structure, then it would be best to choose a carbon fibre pane(light, but rigid in the face of torsional stress) and a titanium frame (also light, but much higher durability than carbon).

The current regulations state that gearboxes must last 4 races, and must consist of between 4 and 7 forward gears and a reverse gear. Teams can still replace the clutch, gear ratios, dog rings, oil filters and hydraulics. This is significant, owing to the fact that most of the gearboxes failures in 2007, particularly with BMW's F1.07, were caused by hydraulic sealings. This may be why the new "4 race" rule has had little effect on reliability in the 2008 season.

Until 2005, all teams used a gearbox that resembled conventional sequential gearboxes that are commonplace in racing series worldwide. Like their manual H pattern counterparts (sometimes referred to as "dog boxes" or "crash boxes") these sequential gearboxes lacked synchros. In most production based cars, a synchromesh is a type of cone clutch, usually machined from brass, that sits between the dog collars of the gearbox's output shaft and the dog teeth of the gears. As a gear is requested, and the selector fork moves the collar to the desired gear, the cone on the side of the gear meets a chamber inside the synchro. The friction between these two components would slowly bring the dog teeth on the side of the gear and the teeth on the side of the collar to the same rotational speed, allowing the next gear to be enganged smoothly to the drive-shaft through the collar.

Because this system relies on friction to get the dogs and gears spinning at the same speed, it is quite slow and not suitable for racing applications. In many racing series, drivers have to double clutch in order to bring the engine RPM to a level where the next gear is being driven at the same speed as the the output shaft. This means pausing during upshifts after the second "clutch-in," and heel & toe-ing during downshifts in order to increase the speed of lower ratios to match the speed of the driveshaft. In F1, this responsibility falls on the ECU. Instead of relying on the friction of the synchros, or the driver to manage the engine speed, the ECU (by either manipulating spark, or fuel) ensures that the gear in the process of being selected is being rotated at road speed.

Another feature that F1 gearboxes (inluding the new SSG designs) share with conventional racing boxes, is the method for moving the selector forks along the output shaft. It is of course these selector forks which move the collars that engage the next gear. When the driver uses a paddle on the steering to effect a gear change, this actuates a hydraulic piston through an electronic linkage, which then activates a "cam and pawl" mechanism. The cam and pawl is responsible for rotating the selector drum. The drum is axial to the output shaft, sitting directly below it. The rings connecting the selector forks rest in grooved pathways around the circumference of the selector drum. The pathways have "curves" or "notches." When the drum rotates such that the ring of a selector fork reaches one of these notches, the selector fork moves a collar along the output shaft, engaging the next gear.

             Gearbox3

Autosport's 2007 technical review also alludes to the fact that all SSG designs continue to have two-shafts(one input and one output) and a single clutch. This is crucial because FIA dogma dictates that a dual clutch system would represent a CVT transmission, and therefore banned. This means that the SSG bears no resemblance to a DSG. A DSG would also have larger packaging implications which make it unsuitable for an F1 chassis. The DSG uses two countershafts, one for each clutch. The second countershaft is rotating inside the hollow centre of the first, and extends the full length of the gearbox. In many dual-clutch gearbox configurations, the following two measures are taken to reduce the length of the gearbox, which are both important space saving features in power trains with a transaxle configuration:

a) There are 2 different output shafts, which each connect to the driveshaft via 2 seperate helical gears. The 2 output shafts have gears 1 through 6 divided between them.
b) The 4th and 6th ratios both use the same gear on the first countershaft as part of their gear pairing.

While these measures are convenient for a transaxle configuration, they drastically increase the width and height of the gearbox, and is therefore counter-productive within the framework of an F1 chassis, because the gearbox must be built as narrowly as possible to maximize space for the diffuser.

                   Gearbox4

In part 2 of this feature we will investigate how the principle behind the SSG allows it to almost instantenously select the next gear, and is effectively in 2 gears at once...

*The 2nd part of the article, which will be coming soon.

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The secrets of Seamless Shift Gearboxes in F1
BMW Sauber F1 (IP Logged)
08/05/2008 17:03
The secrets of Seamless Shift Gearboxes in F1

 
pgj
Re: The secrets of Seamless Shift Gearboxes in F1
pgj (IP Logged)
09/05/2008 09:58
Thank you, that was a very good post.

It seems to be covering 'standard' SSG's though. I have been trying to find out more about Sequential SSG's which some teams are running with. Maybe it will be in the follow up article.

That is the most complete SSG analysis that I have read.

Williams and proud of it.

 
MESSAGES->author
Re: The secrets of Seamless Shift Gearboxes in F1
Raid Phoenix (IP Logged)
09/05/2008 20:08
Awesome article, and the second part (as far as I have said) will be even better winking smiley

Just one thing I didn0t understand at all: could you explain with more detail how the syncronization works in F1 gearbox ( at least in the conventional ones, the pre-2005)?

I know quite well how its done in road cars, but not sure about F1's. You say: "Instead of relying on the friction of the synchros, or the driver to manage the engine speed, the ECU (by either manipulating spark, or fuel) ensures that the gear in the process of being selected is being rotated at road speed" , but there has to be some kind of phisic actuator to the gear discs too. Because that alone, seems more kind of a TC that affects the engine, but not the gearbox itself ( it would be similar to when a driver does a double clutch). Or it would be a bad compromise for the engine, as it would have over or under-rev just before changing the gears, and all that done is a very short period of time.

Friction, as you said its not the best way in highly stressed and high rotation speed pieces like in a F1, so it makes sense to use different device from the road car dogs teeth syncronizers. But which one do they use?

I could guess it would be via hydraulics (using the fluid, oil, as a syncornizer), or it could be with an electric engine (but I doubt it).

Racing against the machine!



Edited 2 time(s). Last edit at 2008:05:09:20:22:09 by J-Raid.

 
pgj
Re: The secrets of Seamless Shift Gearboxes in F1
pgj (IP Logged)
09/05/2008 21:35
I have only heard it explained in layman's terms. I believe that it is done through slipping the disengaged clutch, bringing the disengaged gear set up to speed.

Williams and proud of it.

 
MESSAGES->author
Re: The secrets of Seamless Shift Gearboxes in F1
KineticKid (IP Logged)
09/05/2008 22:58
Thanks for the feedback, pgj.

Jaime: good question.

Quote:
but there has to be some kind of phisic actuator to the gear discs too. Because that alone, seems more kind of a TC that affects the engine, but not the gearbox itself

Not quite true. The ECU performs the same duty that a driver would with a regular racing "crashbox," meaning that it double clutches automatically.

In pre-SSG F1, the car would automatically clutch-in to take the clamping force off the dog teeth of the current gear disc, freeing the collar. It then clutches out, which means the engine is now being used to control the rotation of the gear ratios via the input shaft/countershaft, since the clutch-plates are now fully re-engaged with the flywheel. During upshifts, the engine's RPM is reduced so that the speed of the next gear is slowed to match the speed of the output shaft(drive-shaft) before it is selected, so the dogs can lock smoothly. You could describe it as inter-gear traction control.

The only question that remains is whether there's a need for the ECU to clutch-in a 2nd time when shifting from neutral into the next gear. As you know, at this point a good driver can just jam into the next gear without clutching again if he has matched the revs properly. If the pre-2005 ECUs were precise enough, then they could do the same, as I imagine they did.

A synchro, on the other hand, is responsible for controlling the speed of the gear discs, input shaft and clutch plates when they are NOT connected to the engine, hence the lack of need for double-clutching.



Edited 2 time(s). Last edit at 2008:05:09:23:30:59 by KineticKid.

 
pgj
Re: The secrets of Seamless Shift Gearboxes in F1
pgj (IP Logged)
10/05/2008 09:43
It is a very interesting area. A SSG is in effect two , parallel, gearboxes that get switched and controlled through its own management system. When talking about TC being banned, there is scope for a form of TC to be introduced through this area. Calling it gearbox mapping does not really change the overall effect on the transmission drive from engine to tyre. It is still, a less effective, form of TC.

This is why I am curious to find out how a sequential version of SSG works. Several teams have switched to this form of SSG this year. It interests me why they have gone along this path in the absence on ECU TC. I may be a cynic, but I can't help but feel that they would not have done it if their was not some additional technology involved that helped compensate for the loss of ECU TC.

Sorry for going on. Top notch information, thank you.

Williams and proud of it.

 
MESSAGES->author
Re: The secrets of Seamless Shift Gearboxes in F1
Raid Phoenix (IP Logged)
10/05/2008 13:47
Yeah, you are right KineticKid, I got messed up a bit with my ideas. I confused a couple of them and I was not taking the right thinking approach, mainly because I was thinking in a new concept I'm trying to investigate and mixing ideas too with syncros winking smiley

And I should have not asked at all, since I'm big fan (and praticer) of "heel & toe-ing" even thought its not strictly necessary in nowadays cars.

Still, about the the ECU (by either manipulating spark, or fuel) ensures that the gear in the process of being selected is being rotated at road speed (which also happened with TC and even in fuel mix during SC) I'm not sure of something:

The fuel regulation could have some negative effects, especially knocking and misfiring. Same applies for cutting off the spark ignition. Knocking happens when there is a not desired detonation (that means explosion due to high pressure). That can be especially bad in petrol engines, that use spark provoked explosions (contrary to diesels). One of the main reasons that create the undesired knocking is having a poor mix (that means more air per each part of fuel), and another is the lack of a spark.
Knocking can be extremely bad for the engine, as the detonation flame can expand up to 25 times faster than a normal spark-provoked explosion, and can damage the piston (and if they happen quite a lot can end up with the engine broken). In fact the name comes from the metalic noise created by high frecuency vibrations created by the detonation in the cylinder.
So that case when ECU changes could be a negative effect.

Probably you already knew this, but I'm sure others are enjoyning this discussion too.
So, what do you think, could there be really bad effects with that way of controlling engine rpm and gears changes?

Racing against the machine!

 
MESSAGES->author
Re: The secrets of Seamless Shift Gearboxes in F1
KineticKid (IP Logged)
10/05/2008 14:16
The TC era was marked by misfiring cylinders, and while it came at the expense of engine performance, it was worth it to significantly improve rear wheel traction. It didn't seem to hurt reliability, tho.

There are also some petrol engines which employ compression ignition, not just deisel. It's a relatively new technology. The combustion chambers are re-designed to address the knocking issue caused by detonation at several points around the chamber, (like u mentioned) contrary to spark which is limited to one point in the chamber. It's also proven to speed up combustion, and improve fuel economy. I'm not saying that this means that there wouldn't be a knocking issue in a petrol F1 engine, but this new technology shows that these concerns can be addressed, and may have formed part of F1 engine development over the past years.

And your idea regarding some kind of hydraulic system to syhnchronize the gearbox wasn't a bad one. It would have to be used while the clutch disc is dis-engaged, just as with synchros in a production car. The only problem is the added level of complexity and reliability concerns when it comes to F1 application. Simple is better when it comes to shifting gears at engine speeds of 15 to 20000 rpm.



Edited 1 time(s). Last edit at 2008:05:10:14:18:52 by KineticKid.

 
MESSAGES->author
Re: The secrets of Seamless Shift Gearboxes in F1
Raid Phoenix (IP Logged)
10/05/2008 14:40
Quote:
There are also some petrol engines which employ compression ignition, not just deisel. It's a relatively new technology.

I suppose you mean the HCCI, the new tech that Mercedes and Volkswagen are testing (that uses detonation at low revs and spark explosions at high revs).

I read that they still struggled with uncontrolled detonation, and that the tech could not be used yet, at least in the 5 next years, as that and other problems have to be adressed.

Yet, it looks a promising tech, as Merc had created a 1.8 Turbo engine with over 250hp but with a diesel fuel consumption and with petrol emissions (petrols are better than dieasels in NOx, S and other emissions, excepting CO and CO2)

Quote:
and may have formed part of F1 engine development over the past years.

He, thats one of the points I was trying to arrive to. Is F1 using similar solutions?...

Quote:
The TC era was marked by misfiring cylinders, and while it came at the expense of engine performance, it was worth it to significantly improve rear wheel traction. It didn't seem to hurt reliability, tho.

The reliability thing is what surprises me a bit, especially with the high temperatures reached in a F1 engine, as well as high pressures.
Though, I'm now thinking that both having a short stroke (hence the fuel mix is quite close to the spark) and high revs (as F1 engines) helped preventing knocking.

ANd changing (reducing) the compression ratio (the relation between the combustion chamber and the cylinder displacement) helped too, although it could reduce performance.

I Will investigate a bit, and post more detailed info about it (knocking and misfiring) here.

Racing against the machine!



Edited 1 time(s). Last edit at 2008:05:10:14:41:33 by J-Raid.

 
MESSAGES->author
Re: The secrets of Seamless Shift Gearboxes in F1
Raid Phoenix (IP Logged)
11/05/2008 14:29
Quote:
And your idea regarding some kind of hydraulic system to syhnchronize the gearbox wasn't a bad one. It would have to be used while the clutch disc is dis-engaged, just as with synchros in a production car. The only problem is the added level of complexity and reliability concerns when it comes to F1 application. Simple is better when it comes to shifting gears at engine speeds of 15 to 20000 rpm.

Well I was thinking that as the gears and engine shaft are already being lubricated, by simply changing the level of oil going to them, you could slightly change their speed, hence doing like a syncro.

I don't think it would be a big deal for complexity, but I agree that it could be bad for reliability, especially if there is less oil going.

Could you explain how the oil is used in SSG or conventional F1 gearboxes?

I know quite well how it is used in engines (all the wet, dry and semi-dry sump stuff), but not so much in gearboxes. Is it "inundated" with oil, or is it inyected with high pressure but small flow? SOmething intermediate?

Racing against the machine!

 
MESSAGES->author
Re: The secrets of Seamless Shift Gearboxes in F1
KineticKid (IP Logged)
14/05/2008 00:11
Quote:
Is it "inundated" with oil, or is it inyected with high pressure but small flow? SOmething intermediate?

This will have to be the subject of further investigation winking smiley

I would think that a smaller flow would be the goal because you would get less power loss with lower immersion. And a more precise injection system ensures proper lubrication at such high rotational speeds.

Something I forgot to mention in the article is that it's only been 4 or 5 years since many of the teams switched to a dry sump for the gearboxes...

 
pgj
Re: The secrets of Seamless Shift Gearboxes in F1
pgj (IP Logged)
14/05/2008 15:23
A really good thread, thank you.

Williams and proud of it.

 
MESSAGES->author
Re: The secrets of Seamless Shift Gearboxes in F1
Raid Phoenix (IP Logged)
14/05/2008 17:01
Quote:
I would think that a smaller flow would be the goal because you would get less power loss with lower immersion. And a more precise injection system ensures proper lubrication at such high rotational speeds.

Yeah, probably they use a similar system to the engine (which is with high pressure injectors and similar devices).
In fact road car engines have moved from almost totally inmersed lower part of the crankshaft to to current wet sumps and then they are moving to semi-dry or dry sumps.

Quote:
Something I forgot to mention in the article is that it's only been 4 or 5 years since many of the teams switched to a dry sump for the gearboxes...

So, before they used wet ones, or semi-dry sumps?
For example Lamborghini use semi-dry sumps in their race cars and works very well for them...

Racing against the machine!

 
pgj
Re: The secrets of Seamless Shift Gearboxes in F1
pgj (IP Logged)
14/05/2008 18:21
This is going off the original thread a bit, but how does a dry sump work? Is it a continuously pumped system?

Williams and proud of it.

 
MESSAGES->author
Re: The secrets of Seamless Shift Gearboxes in F1
Raid Phoenix (IP Logged)
14/05/2008 18:58
Check this links:
http://en.wikipedia.org/wiki/Dry_sump

http://auto.howstuffworks.com/question331.htm

http://auto.howstuffworks.com/engine2.htm

I will bring you my own explanation too (as at the moment I'ms studying Internal combustion engines at uni, and investigate about it too) asap winking smiley

Racing against the machine!

 
pgj
Re: The secrets of Seamless Shift Gearboxes in F1
pgj (IP Logged)
14/05/2008 22:12
Thank you.

Williams and proud of it.



Edited 1 time(s). Last edit at 2008:05:16:09:26:40 by pgj.

 
MESSAGES->author
Re: The secrets of Seamless Shift Gearboxes in F1
KineticKid (IP Logged)
15/05/2008 22:37
Quote:
So, before they used wet ones, or semi-dry sumps?
For example Lamborghini use semi-dry sumps in their race cars and works very well for them...

Wet sump, since the main pump was located in the oil pan and didn't pump the oil through seperate reservoirs.

Although, there's obviously a limit to how much you can compare the engine system to a gearbox system when using either term(wet or dry).

 
ulisse di bartolomei
Fiat patent fraud
ulisse di bartolomei (IP Logged)
10/11/2010 20:54
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If the industries can afford unpunished to copy the ideas and defending it need very expensive trial, to which target need the patents? How our young people can find intellectual courage if the economic potentates crush the rights of the single ones? How to defend the rights of private inventors? Whoever is about to ask for a patent or wants to propose a proper patent to a great firm I suggest to give a look to my experience with the Fiat, to get able to operate with best adroitness. Thanks and good time to everybody. Ulisse Di Bartolomei

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